Galvanic replacement goes universal!

It's been a while since we enjoyed a nano breakthrough. But recently, May 24th to be exact, Prof. Taeghwan Hyeon (Oh et al., Science, 340, 964) and his group at Seoul National University took the galvanic exchange method of making nanocages (e.g. see Prof. Younan Xia's seminal work on gold nanocages) and applied to metal oxides. They successfully made boxes of iron oxides by mixing Fe³⁺ with Mn₃O₄ nanocubes. This is a major expansion of the galvanic exchange methodology and certainly we'll see a trillion other examples, since metal oxides are much more abundant and stable than metallic counterparts (in case you forget, just think about our oxygen rich atmosphere). Congrats to Hyeon and Nicola Pinna (a WCU prof. at SNU) for another spectacular discovery!   

Catalytic mysteries are being unraveled through Gold clusters

No wonder why clusters are important. These days a cluster means a tinier nanoparticle. You can actually count the atoms. Herzing et al. (Kiely group at Lehigh) showed us how a cluster can unravel mysteries of the catalysis world.

Gold clusters with 10 atoms (~0.5 nm) on iron oxide (FeOOH and Fe2O3) are found to oxidize CO 100% at 25 oC. Though gold (Au) is known to catalyze oxidation reaction in good yields, the unusual observation was that the smaller wasn't always the better. In fact atomic gold or monolayer gold was doing poorly as compared to bilayer clusters of 10 atoms. The article was well written and the discussions are satisfactory, however, the technique they relied on left some suspicion on several of us. The "High-magnification aberration-corrected STEM-HAADF images" were the basis of their arguments and it's very tricky to get reliable data (see the earlier post here).

Cutting graphene with in-situ formed iron (Fe) nanoparticles

Datta et al. (from Johnson group of UPenn) utilizes iron nanoparticles (~15 nm) and the catalytic formation of methane from carbon and hydrogen in the scission of the thin graphene layer. Iron nanoparticles are formed by spraying iron nitrate (Fe(NO₃)₃.9H₂O) onto the graphene and cooking it under reductive Ar atmosphere (Ar + H₂). This is an important step in graphene related technology though it very much resembles the 2006 carbon nanotube seeds study (noted for placing Rick Smalley as the first author since it was published soon after his death). In the images, FLG is Few-Layer Graphene and the scale bar is 800 nm.